Diaphragm for sound reproduction



Oct. 21 1924.

- F. A. E. JENKINS DIAPHRAGM FbR scum) iREPRODUCTION Filed March 27 1924- B I F Cofirrgaresgeiand C Pan e Patented Oct. 21, 1924.

UNITED STATES PATENT OFFICE.

FREDRICK ALFRED EDWARD JENKINS, OF SYDNEY, NEW SOUTH WALES, AUSTRALIA.

DIAPHRAGM FOR SOUND REPRODUCTION.

Application filed March 27, 1924.. Serial No. 702,466.

To all whom it may concern:

Be it known that FREDRIGK ALFRED ED This invention relates to the construction of diaphragms for sound reproduction such as those used in talkin machines and such instruments and the obyect of theinvention is to provide a diaphragm of uniform thickness and tension which will .give a clearer and more natural reproduction" of sound than any other diaphragm at present in use and which will not be effected by cilmatic changes and; which will not shatter under continued vibration.

A further object is to provide a diaphragm which will not set u any sound of itself when vibrated and which will be free from any false vibration, but will truly and effectively reproduce the vibrations transmitted to it.

The invention comprises a tympan or membrane, a metal ring adapted to grip this membrane evenly and subject it to uniform tension, and a resilient compound moulded round the ring to form a coat-ing thereon to insulate the metal ring and membrane from the sound box.

The tympan or membrane is constructed of a plurality of very thin discs or sheets of suitable wood having, if desired, intermediate layers of light silk or similar material.

These sheets and layers are superimposed in such a manner that the grain or warp of no two sheets or layers is parallel and are rendered water proof and cemented or glued together under pressure to form a tympan or membrane of uniform thickness, strength and resiliency in every direction.

The trimmed membrane is then placed within a metal ring of L section so that it is retained by the horizontal member of the L. The vertical member is then hammered inwards to grip the membrane between the jaws of a ring of U section.

The ring is then caused to grip the membrane tightly and uniformly and is expand ed outwardly to exert a uniform tension in all directions on the tympan. The ring also prevents warping 'or twisting of the membrane. I

In order to insulate the metal ring surrounding the tympan or diaphragm and provide a resilient seating for same within the sound box an enveloping ring of rubber or rubber compound or other relisient compound such as a mixture of glycerine and gelatine is moulded round the ring and is allowed to encroach slightly on the membrane to prevent the vibration from extending to the metal ring.

In the drawings which illustrate a method of constructing a diaphragm according to this invention,

Figure 1 is a diagrammatic elevation of a press for building up the membrane.

Figure 2 is a diagrammatic plan of same.

Figure 3 is a sectional elevation showing the membrane placed in the retaining ring of L section.

Figure 4 shows the complete membrane and ring.

Figure 5 is a sectional elevation of a mould for placing the resilient sound insulating material round the ring, and

Figure 6 is a sectional elevation of the complete improved diaphragm.

Fig. 7 is a plan view of the diaphragm partly in section and before the resilient ring has been placed on the same.

The membrane or tympan 7 is built up of a plurality of layers 8 of wood reduced to the thickness of fine paper with or without intermediate layers of fine silk or a similar material superposed on the lower member 9 of a press in such a manner that the grain or warp of no two layers is parallel. For example if it is considered that six layers of material are necessary for a particular membrane the grain or warp of the first would be along the line A A and the second would be along the line B B and so on till the sixth layer would have its grain or warp along the line F F, see Figure 2.

The layer or sheets are glued or'cemented together under pressure bet-ween the members 9 and 10 of the press. The complete membrane is also rendered impervious to moisture by any well known means. either before being built up or when completed.

After being cut and trimmed to the desired size the membrane 7 is placed in the ring 11 as shown in Figure 3 so that it is supported by the horizontal member of the L. The vertical member is then turned downwards to; clamp the membrane as shown in Fig. 4, and is at the same time expanded e fl fe'nte ens-'1 may b f ny uitable ma er a 1 1 s. f fiber r be omp itionb lfi s, Pre erab y a ur e ye r he and. s itia e hepr o t of 8 part wr e i .91 12 i? q elet ee r fique i r f web,

-'An mp e cemp e e cl aphra mr er I. l im sound reproduetion comprising membrane edadin Several. sup rpe -d Water-proo bi 'eheets i W od; t e e a ee j' h t being arranged at angles to the grain of the her she an th grain awe sheet being p allel 9- li es radi tes a eq alierr -1 r m c m peint a me a g of U-seotion gripping the edgeportion of the membrane and holding it taut, and a ring of resilient material formed around said metal ring and encroaching slightly on said membrane.

2. In a diaphragm for sound reproduction, a membrane including several superposed Water-proofed thin layers ofwood, the grain I of each layer being arranged at angles to the grain of the other layers and the grain of the layers being parallel to lines radiating at equal intervals from a common point a;

metal ring of U-seotion gripping the peripheral edge portion of the membrane and holdingit taut, and a resilient-ring arranged around and ent rely enclosing said metal lid eemp si iqn f l'a an g y n In, est mony vher' ief hef asfe'ifi e s,

nat r PIQSQDC f two itnesses; REDRKK ALFRED- EDWARDJENKl-NS;

' Witnesses:

1 ring, said resilient ring beingformed ofal 

